This invention relates to constant volume flow controls of the type used to maintain a relatively constant rate of discharge from a terminal of an air distribution system or the like, and more particularly to an improved regulator for a damper assembly operable to control the flow of conditioned air whereby the regulator has a relatively large operational range of constant volume settings.
Many multi-room structures, such as office buildings and schools, constructed during the past several years include air conditioning systems to deliver either relatively warm or cool conditioned air from a central source thereof to each of the enclosures or rooms in the building. Typically, one or more ducts are employed to deliver the air to each enclosure. Very often a damper assembly or similar mechanism is installed in the duct to regulate the flow of air to one or more diffusers or discharge outlets located in the enclosure being conditioned by the discharge of air thereinto. The movement of the damper assembly may be responsive to changes in the conditioned air supply pressure and/or changes in the temperature of the enclosure. The controls regulating movement of the damper assembly typically include control point setting means establishing a maximum level of conditioned air flow irrespective of changes in the supply air pressure.
Constant volume flow controls of various constructions employed with air conditioning systems of the above-described type are well known in the art. Very often, a spring or similar force generating means is employed in obtaining the predetermined volume flow setting. One of the shortcomings of the prior art devices is that with a particular spring, the control point setting means is only effective over a relatively narrow range of flow rates. When rates outside of that range are to be accommodated, it is necessary to substitute a spring of a different characteristic for the spring already used.
In U.S. Pat. No. 3,506,038, issued in the names of Leo F. Perry and Joseph W. Spradling, an attempt has been made to solve the problem. The cited United States patent discloses the use of a first torsional spring to generate a force opposing the movement of the damper assembly. A second torsional spring is used to generate a force on a valve blade. The valve blade is movable relative to the damper assembly. The position of the valve blade determines the constant volume flow setting for the system. The disclosed arrangement has an operating range of 250-500 cfm, or a 50% control range. However, in some applications, it has been found advantageous to have a much greater range than the 50% range available through the arrangement of the prior art patent. For example, in some applications, a useful control range of 50 to 500 cfm is required. With the arrangement disclosed in the cited patent, it would be necessary to substitute two pairs of springs having different characteristics to obtain the same operating range as that achieved via the present invention.